The invention relates to a manhole covering, particularly for sewers, gullies and water intakes and which is laid at the mouth of a preferably vertical manhole and has a frame or a casing embedded in the ground and a base frame for mounting a manhole cover or grating, which is provided with adjusting means enabling the adjustment in height and inclination of the base frame.
The present invention is in the field of the construction and covering of manholes, as well as the draining off of rainwater and other liquids, for constructions of all types, particularly highways, squares and bridges. The top layer is generally formed of bitumen, concrete or cement, under which there is a foundation, which can be made from different materials such as gravel, sand, concrete, etc. Between the foundation and the top layer in many cases, e.g. bridges and roadways, is provided a sealing sheet to protect the foundation from penetration of moisture.
The rainwater and other liquids falling on constructions must be drained off and, for this purpose, sewers and water intakes of various types are used. The openings of such sewers and intakes must be covered by a manhole covering, which essentially comprises a manhole frame and a manhole cover or grating inserted therein. During the first laying of such a covering the manhole frame is laid flush with the ground surface, which is necessary to permit unimpeded walking or traveling thereover.
In the case of highways and squares the problem occurs that the top layer has to be partly or completely replaced. However, it is not then generally possible to maintain the original surface level, which means that the manhole frame must be raised or lowered to the new level of the top layer. This is a complicated matter, which involves high costs and also an undesired restriction of the traffic flow. The same problem occurs in the reconstruction of roads, because in general the final level is not precisely known. The adjusting of the height and slope can also take place before or after laying the top layer. This problem has long been known and numerous proposals have already been made for reducing the effort and expenditure for a realignment of the shaft frame following the laying of a new top layer.
An important requirement in connection with such adjustable manhole frames is not only to position such a frame in different positions, but also to reliably maintain it there, so that even when heavy traffic travels over it, it cannot undergo any upward displacement. In addition, the insertion and removal of the adjusting device must be easy.